1. Field
The present invention relates to a method and apparatus for idle speed control based on variable torque converter load.
2. Description of the Related Art
A conventional automobile has an engine which remains operative, even when a gas pedal is not depressed. That is, the engine operates at a target idle engine speed. This is because the engine needs to keep running at a certain level to prevent the engine from stalling, and also to provide energy to accessory devices in the automobile which may require energy to function. To keep the engine running, a throttle allows a certain amount of airflow to enter the engine so that the engine can use the airflow to combust fuel. Control of the airflow results in control of the operational conditions of the engine.
Conventionally, the amount of airflow allowed to operate the engine at a target idle speed is set by the manufacturer and not adjusted or capable of adjustment. Such airflow to prevent the engine from stalling and idle at the target speed was combined with the airflow required to compensate for the energy required from the accessory devices in the automobile. However, this did not take into account the fact that the amount of airflow required to operate the engine at a target idle speed can vary with a number of conditions, including vehicle speed. For example, as an automobile goes into motion, the resistance from a torque converter can decrease to zero. That is, under certain conditions, the engine encounters little resistance when operating, needs to combust less fuel to overcome the resistance, and thus requires very little airflow.
Without taking into account such diverse situations for operating the engine, too much airflow is sometimes supplied to the engine. This results in the engine combusting more fuel than necessary to operate at the target idle speed. Since fuel economy for an automobile is one of the major considerations for an automobile purchase, this can reduce the conventional automobile's competitiveness in the marketplace. Furthermore, since government regulations for fuel economy has increasingly become tighter, this fuel inefficiency can also cause design problems.
Also, the consumption of more fuel can also directly affect an amount of emissions from the conventional automobile, which again can reduce the conventional automobile's competitiveness in the marketplace and may also cause design problems. From a national standpoint, increased fuel consumption may be undesirable for many reasons, some of which relate to national security and also environmental protection.
Thus, there is a need for a method and apparatus for idle speed control based on variable torque converter load.